2 Answers from Attorneys

The U.S. Code is not part of the Constitution. I'm not sure what you mean by "USC 31". You could mean Title 31 of the U.S. Code, or you could mean section 31 of any of the 51 titles. You might even mean Title 31 of the Code of Federal Regulations, which is related to Title 31 of the Code.

You probably mean Title 31 of the U.S. Code. That title deals with money and finance. But the title has 28 chapters consisting of hundreds of statutes. Most of those statutes are not criminal, but some include criminal provisions. For example, 31 USC § 5324 makes it a crime to fail to file various types of reports, or to cause or attempt to cause such failures by various institutions.

As for the other part of your question, the U.S. Code is not "part of" the U.S. Constitution, but the Article VI of U.S. Constitution does refer to it, stating, in part:

"This Constitution, and the laws of the United States which shall be made in pursuance thereof; and all treaties made, or which shall be made, under the authority of the United States, shall be the supreme law of the land; and the judges in every state shall be bound thereby, anything in the Constitution or laws of any State to the contrary notwithstanding."

The U.S. Code contains "the laws of the United States which shall be made in pursuance" of the Constitution.